U.S. patent application number 15/550226 was filed with the patent office on 2018-02-01 for apparatus for ascertaining and monitoring a fill level.
The applicant listed for this patent is Endress+Hauser GmbH+Co. KG. Invention is credited to Thomas Blodt.
Application Number | 20180031406 15/550226 |
Document ID | / |
Family ID | 55275074 |
Filed Date | 2018-02-01 |
United States Patent
Application |
20180031406 |
Kind Code |
A1 |
Blodt; Thomas |
February 1, 2018 |
APPARATUS FOR ASCERTAINING AND MONITORING A FILL LEVEL
Abstract
The invention relates to an apparatus for transmitting and
receiving electromagnetic waves (EM waves) for ascertaining and
monitoring a fill level of a medium in a container, comprising a
first hollow conductor with a first coupling element for the out-
and in-coupling of EM waves, a second hollow conductor with a
second coupling element for the out- and in-coupling of EM waves, a
horn radiator for radiating and focusing of EM waves, wherein the
first and second hollow conductors are dimensioned such that EM
waves out-coupled from the first and second coupling elements
radiate from the horn radiator scattered and with weak intensity,
or scattered and weak intensity EM waves, which are received from
the horn radiator, couple to the first and second coupling
elements, and EM waves out-coupled only from the first coupling
element radiate from the horn radiator focused and with strong
intensity, or focused and strong intensity EM waves, which are
received from the horn radiator couple only to the first coupling
element.
Inventors: |
Blodt; Thomas; (Steinen,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Endress+Hauser GmbH+Co. KG |
Maulburg |
|
DE |
|
|
Family ID: |
55275074 |
Appl. No.: |
15/550226 |
Filed: |
January 27, 2016 |
PCT Filed: |
January 27, 2016 |
PCT NO: |
PCT/EP2016/051679 |
371 Date: |
August 10, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01Q 13/02 20130101;
G01F 23/284 20130101; H01Q 1/225 20130101; H01Q 13/025
20130101 |
International
Class: |
G01F 23/284 20060101
G01F023/284; H01Q 13/02 20060101 H01Q013/02; H01Q 1/22 20060101
H01Q001/22 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 12, 2015 |
DE |
10 2015 102 002.5 |
Claims
1-10. (canceled)
11. An apparatus for transmitting and receiving electromagnetic
waves (EM waves), comprising: a first hollow conductor including a
first coupling element embodied to out-couple and to in-couple EM
waves, the first hollow conductor having a first end face that is
closed and a second end face that is open, so that EM waves that
out-couple via the first coupling element are transmitted via the
second end face, and so that EM waves that are received via the
second end face in-couple to the first coupling element; a second
hollow conductor including a second coupling element embodied to
out-couple and to in-couple EM waves, the second hollow conductor
having a first end face that is open and a second end face that is
open, wherein the first end face of the second hollow conductor
borders on the second end face of the first hollow conductor, so
that EM waves transmitted from the first hollow conductor are
transferred by the second hollow conductor, and so that EM waves
transferred by the second hollow conductor are received by the
first hollow conductor; and a horn radiator embodied to radiate and
to focus EM waves, wherein an intake opening of the horn radiator
communicates with the second end face of the second hollow
conductor, so that EM waves transmitted from the second hollow
conductor are radiated from the horn radiator, and so that EM waves
received from the horn radiator are focused into the second hollow
conductor, wherein the first hollow conductor is embodied such that
first electromagnetic wave modes are producible in the first hollow
conductor, wherein the second hollow conductor is embodied in such
a way that second electromagnetic wave modes are producible in the
second hollow conductor, wherein the first hollow conductor and the
second hollow conductor are dimensioned such that: EM waves
out-coupled from the first coupling element and the second coupling
element radiate from the horn radiator scattered and having a weak
intensity; scattered and weak intensity EM waves that are received
from the horn radiator couple to the first and second coupling
elements; EM waves out-coupled only from the first coupling element
radiate from the horn radiator focused and having a strong
intensity; and focused and strong intensity EM waves that are
received from the horn radiator couple only to the first coupling
element.
12. The apparatus as claimed in claim 11, wherein the first hollow
conductor is at least partially filled with a first dielectric
material and the second hollow conductor is at least partially
filled with a second dielectric material.
13. The apparatus as claimed in claim 12, wherein a dielectric
constant of the first dielectric material is smaller than a
dielectric constant of the second dielectric material.
14. The apparatus as claimed in claim 13, wherein a ratio between
the dielectric constant of the second dielectric material and the
dielectric constant of the first dielectric material is about 2.5
to 1.
15. The apparatus as claimed in claim 11, wherein a separation
between the first coupling element and the second coupling element
in a transmission direction of the EM waves corresponds to 3/4
.lamda.+n.times..lamda./2, wherein .lamda. is a wavelength of the
EM waves and n is a natural number 0, 1, 2, . . . .
16. The apparatus as claimed in claim 11, wherein a length of the
first coupling element is less than or equal to .lamda./4 and a
length of the second coupling element is less than or equal to
.lamda./2, wherein .lamda. is a wavelength of the EM waves.
17. The apparatus as claimed in claim 11, wherein the first
coupling element includes a first terminal embodied to transfer EM
waves that out-couple or in-couple at the first coupling element,
and wherein the second coupling element includes a second terminal
embodied to transfer EM waves that out-couple or in-couple at the
second coupling element, the apparatus further comprising a voltage
divider disposed between the first terminal and the second terminal
and embodied to divide the EM waves between the first coupling
element and the second coupling element.
18. The apparatus as claimed in claim 17, wherein the voltage
divider includes an electrical capacitance and a bandpass
filter.
19. The apparatus as claimed in claim 17, wherein the voltage
divider includes a capacitance and a diode.
20. The apparatus of claim 17, wherein the voltage divider includes
a capacitance and an oscillatory circuit.
21. The apparatus as claimed in claim 17, wherein the voltage
divider is a capacitive voltage divider.
22. The apparatus as claimed in claim 19, wherein the diode is a
varactor diode.
Description
[0001] The invention relates to an apparatus for transmitting and
receiving electromagnetic waves (EM waves) for ascertaining and
monitoring a fill level of a medium in a container by means of
travel times of EM waves.
[0002] Conventional pulse radar, fill level measuring devices have
regularly a transmission system having a pulse producing system
connected to a control unit. The pulse producing system produces
for each measurement a transmission signal, which is composed of
microwave pulses of a fixedly predetermined center frequency and a
predetermined pulse repetition rate. The microwave pulses have, for
example, fixedly predetermined center frequencies of 26 GHz or 78
GHz. The antenna is mounted on the container above the highest fill
level to be measured, oriented toward the fill substance and sends
the transmission signals into the container. Subsequently, the
antenna receives as received signals the signal fractions reflected
on the fill substance back toward the fill-level measuring device
after a travel time dependent on the distance to the fill
substance. The received signals are fed to a signal processing
system connected to the transmission system and to the antenna, and
the signal processing system determines the fill level based on the
received signals.
[0003] In such case, measurement curves are regularly derived,
which show the amplitudes of the received signals as a function of
their travel time required for the path to the fill substance and
back. From the travel times of the peaks of these measurement
curves, then, based on the propagation velocity of the microwave
pulses, the distance of the fill substance from the fill-level
measuring device can be determined.
[0004] For fill level measurement today, a large number of
different evaluation methods, frequently referred to as echo
recognition methods, are applied, with which the measurement curves
are used to ascertain which peak is to be attributed to the
reflection on the surface of the fill substance. For example, the
first occurring peak or the peak having the greatest amplitude can
be selected as the peak of the particular measurement curve to be
attributed to the reflection on the surface of the fill substance.
From the travel time associated with this peak, based on the
propagation velocity of the microwave pulses, the distance of the
surface of the fill substance from the fill-level measuring device
is derived, which then, based on the installed height of the
antenna, is convertible into the fill level--thus the fill level of
the fill substance in the container.
[0005] These fill level measuring devices deliver reliable
measurement results in a large number of different applications.
For fill level measurement of bulk goods, however, such measuring
devices are, as a rule, not optimally suitable, since bulk goods
regularly form hill and valley shaped bulk goods cones, whose
surface profile is not registered with these fill-level measuring
devices, so that a surface profile cannot be taken into
consideration for the fill level determination.
[0006] Likewise, in given cases, problematic is the use of
conventional fill level measuring devices with a single, rigidly
mounted antenna in applications, in which objects (hereinafter
referred to as disturbances) installed in the container protrude
laterally into the beam path of the transmission signals. Thus
objects, such as other measuring devices or filling nozzles, are
present.
[0007] DE 102012109101 A1 describes a fill-level measuring device
for measuring a fill level of a fill substance in a container. Such
fill-level measuring device includes an antenna, which sends
transmission signals with different center frequencies into the
container, and receives as received signals their signal fractions
reflected back in the container in the direction of the antenna.
Furthermore, the antenna has different spatial radiation
characteristics for different center frequencies depending on the
center frequencies of the transmission signals. A signal processing
system evaluates the received signals based on the center
frequencies of the microwave pulses of the associated transmission
signals and the center frequency dependence of the spatial
radiation characteristics of the antenna.
[0008] Disadvantageous in the case of such a fill-level measuring
device is that the center frequencies of the transmission signals
must be changed, in order to change the radiation characteristics
of the microwave pulses of the transmission signals. That means
that the transmission signals of such fill-level measuring devices
are broadband signals.
[0009] Fill level measuring devices with broadband transmission
signals are not able to resolve the separation between the antenna
and the fill substance finely and therefore are not able to
determine the fill level as exactly as might be desired.
[0010] An object of the invention is to provide an apparatus, which
can determine the fill level of a medium in a container
precisely.
[0011] The object is achieved by the subject matter of the
invention. The subject matter of the invention is an apparatus for
transmitting and receiving electromagnetic waves (EM waves) for
ascertaining and monitoring a fill level of a medium in a container
by means of travel times of EM waves. The apparatus comprises a
first hollow conductor with a first coupling element for the out-
and in-coupling of EM waves, wherein a first end face of the first
hollow conductor is closed and a second end face of the first
hollow conductor is open, so that EM waves, which out-couple via
the first coupling element, are transmitted across the second end
face, and EM waves, which are received across the second end face
of the first hollow conductor, in-couple to the first coupling
element, at least a second hollow conductor with a second coupling
element for the out- and in-coupling of EM waves, wherein first and
second end faces of the second hollow conductor are open, and
wherein the first end face of the second hollow conductor borders
on the second end face of the first hollow conductor, so that EM
waves transmitted from the first hollow conductor are transferred
by the second hollow conductor and EM waves transferred by the
second hollow conductor are received by the first hollow conductor,
a horn radiator for radiating and focusing of EM waves, wherein an
intake opening of the horn radiator communicates with the second
end face of the second hollow conductor, so that EM waves
transmitted from the second hollow conductor are radiated from the
horn radiator and EM waves received by the horn radiator are
focused into the second hollow conductor, wherein the first hollow
conductor is embodied in such a way that first electromagnetic wave
modes are producible in the first hollow conductor, wherein the
second hollow conductor is embodied in such a way that second
electromagnetic wave modes are producible in the second hollow
conductor, wherein the first and second hollow conductors are
dimensioned in such a way that EM waves out coupled from the first
and second coupling elements radiate from the horn radiator
scattered and with weak intensity, or scattered and weak intensity
EM waves, which are received by the horn radiator, couple to the
first and second coupling elements, and EM waves out-coupled only
from the first coupling element radiate from the horn radiator
focused and with strong intensity, or focused and strong intensity
EM waves, which are received by the horn radiator, couple only to
the first coupling element.
[0012] A weaker focusing is achieved by a second, optionally added
mode, which by superpositioning on a first fundamental mode results
in a spreading of the radiation lobe. This second wave mode can be
added by a small control voltage MV. The control voltage MV amounts
to few volts (e.g. 1 . . . 4 V) and the electrical current draw
required in such case lies in the micro-ampere range or lower.
[0013] By switching between narrow and wide lobes--especially in
the case of embodiments with adjustable broadening--some
disturbances can be identified as regards distance, since these in
the case of narrow lobe less appear strongly or even do not appear,
as compared with the wide lobe case. This is beneficial especially
in the case of radar systems with rather lower operating frequency
(e.g. 6 GHz or 10 GHz). Such a switching is beneficial in the case
of wave surfaces, and disturbing, installed objects in the case of
low fill levels as well as in the case of plausibility calculations
in the case of reclined, cylindrical tanks, which produce strong
reflections. Furthermore, an option is periodically to register the
complete measuring range using a broad lobe, and, especially with a
FMCW radar system, then to register exactly with narrow lobe only
the distance range, in which the fill level is to be expected.
[0014] In an advantageous further development, the first hollow
conductor is at least partially filled with at least a first
dielectric material and/or the second hollow conductor is at least
partially filled with at least a second dielectric material. In
this way, hollow conductors with smaller diameters can be used.
Additionally, a protective cap on the broad end of the horn can be
omitted, since the in-coupling element is sealed by the filling
material.
[0015] In an advantageous further development, the at least first
material has a smaller dielectric constant than the at least second
material. In order by means of the apparatus of the invention to
irradiate a large region, it is advantageous to choose the diameter
of the second hollow conductor greater than the diameter of the
first hollow conductor. If the second hollow conductor is filled
with a dielectric material, then it can be dimensioned smaller. In
this way, the diameters of the first and second hollow conductors
can be selected to be equal, whereby the apparatus is simpler to
manufacture and the first and second coupling elements are located
in a shared plane. In this way, the first and second coupling
elements can be arranged on lands of a single circuit card, in
which case the circuit card extends to the antenna apparatus.
[0016] In an advantageous variant, a ratio between the at least
second dielectric constant and the at least first dielectric
constant is about 2.5. In this way, the diameter of the first and
second hollow conductors can be selected to be equal, wherein the
difference between the smallest possible radiation angle and the
greatest possible radiation angle can be enlarged.
[0017] In an advantageous variant, a separation S between the first
and second coupling elements in a transmission direction of the EM
waves corresponds to 3/4.lamda.+n.times..lamda./2, in the case of
which .lamda. is the wavelength of the EM waves and n is a natural
number 0, 1, 2, . . . . In this way, a constructive
superpositioning of the waves out- or in-coupled via the first and
second coupling elements results.
[0018] In an advantageous form of embodiment, a length of the first
coupling element amounts at most to .lamda./4 and a length of the
second coupling element amounts at most to .lamda./2. By setting
upper limits of the lengths of the first and second coupling
elements, it is achieved that in the first coupling element as much
as possible a fundamental mode is excited and in the second
coupling element a mode of higher order is excited. Another
dimensioning of the first and second coupling elements would give a
less favorable reflection at the first end face of the first hollow
conductor.
[0019] In an advantageous form of embodiment, the first coupling
element includes a first terminal for transferring of EM waves,
which out- or in-couple at the first coupling element, wherein the
second coupling element includes a second terminal for transferring
of EM waves, which out- or in-couple at the second coupling
element, wherein between the first and second terminals a voltage
divider, especially a capacitive voltage divider, is provided, such
that the voltage divider determines the dividing of the EM waves
between the first and second coupling elements.
[0020] In an advantageous embodiment, the voltage divider includes
an electrical capacitance and a bandpass filter. The dividing of
the electrical power between the first coupling element and the
second coupling element can be set by the ratio of the impedance of
the second capacitance to the impedance of the bandpass filter.
[0021] In an advantageous embodiment, the voltage divider includes
a second capacitance and a semiconductor element, preferably a
diode, especially preferably a varactor diode. The diode is
advantageously a capacitance diode. The diode is typically so
constructed that the electrical capacitance of the diode changes
especially as a function of the size of the reverse bias. Since the
ratio of the second capacitance to the capacitance of the bandpass
filter governs the dividing of the power between the first and
second coupling elements, thus, variation of the reverse bias
voltage can tune the dividing of the power between the first and
second coupling elements. The second capacitance acts as highpass
filter, i.e. it is a barrier for the reverse bias voltage but lets
wave signals pass.
[0022] In an advantageous variant, the voltage divider includes a
second capacitance and an oscillatory circuit. Instead of a
bandpass filter, an oscillatory circuit can also be used. An
oscillatory circuit is distinguished by a very large change of
amplitude as a function of frequency, in case the frequency is
selected to be in the range including the resonant frequency. In
this way, with a small capacitance change--and, thus, a small
maximum reverse bias voltage on a diode--a large variation of the
dividing of the power between the first and second coupling
elements and, thus, variation of the radiation angle of the EM
waves can be achieved. In order at equal voltage change to bring
about a greater capacitance change in the diode, also a diode with
stronger doping can be used.
[0023] The invention will now be explained in greater detail based
on the appended drawing, the figures of which show as follows:
[0024] FIG. 1 a schematic view of an apparatus 1 of the invention
for transmitting and receiving EM waves, including an electrical
circuit for operation of the apparatus 1,
[0025] FIGS. 2a-2d schematic views of radiations of EM waves from
an apparatus 1 as in FIG. 1 in the case of different designs of the
electrical circuit,
[0026] FIG. 3 a schematic view of an additional embodiment of the
apparatus 1, in the case of which a voltage divider of the
electrical circuit is capacitive, and
[0027] FIG. 4 a schematic view of an additional embodiment of the
apparatus 1, in the case of which the horn radiator is conically
embodied.
[0028] FIG. 1 shows an apparatus of the invention 1 for
transmitting and receiving electromagnetic waves (EM waves) for
ascertaining and monitoring a fill level of a medium (not shown) in
a container (not shown) by means of travel times of EM waves.
Apparatus 1 includes a first hollow conductor 2 with a first
coupling element P1 for the out- and in-coupling of electromagnetic
waves, wherein a first end face 3 of the first hollow conductor 2
is closed and a second end face 4 of the first hollow conductor 2
is open. In this way, EM waves, which out-couple via the first
coupling element P1, can be transmitted via the second end face and
EM waves, which are received via the second end face of the first
hollow conductor 4, can in-couple at the first coupling element P1.
The first hollow conductor 2 is cylindrically embodied and has a
diameter, which is dimensioned in such a manner that only a
fundamental mode is excited. Preferably the fundamental mode is a
mode with a very low cutoff frequency, especially a TE01 mode. The
first hollow conductor 2 can, however, also have an elliptical,
quadratic, n-polygonal or u-shaped footprint.
[0029] Furthermore, the apparatus 1 includes a second hollow
conductor 5 with a second coupling element P2 for the out- and
in-coupling of EM waves, wherein the first and second end faces 6,
7 of the second hollow conductor 5 are open. In such case, the
first end face 6 of the second hollow conductor 5 borders the
second end face 4 of the first hollow conductor 2, so that EM waves
transmitted from the first hollow conductor 2 are transferred by
the second hollow conductor 5 and EM waves transferred by the
second hollow conductor 5 are received by the first hollow
conductor 2. The second hollow conductor 5 can be cylindrically
embodied. The second hollow conductor 5 can have a footprint, which
is square, elliptical, n-polygonal or u-shaped. The second hollow
conductor 5 is designed in such a manner that a higher mode is
excited than the mode in the first hollow conductor 2. The higher
modes can be e.g. a TM11-, TE21-, TE11- or TM21 mode.
[0030] Furthermore, the apparatus 1 includes a widened horn
radiator 8 for radiating, receiving and focusing of EM waves. An
intake opening of the horn radiator 8 communicates with the second
end face 7 of the second hollow conductor 5, so that EM waves
transferred from the second hollow conductor 5 are radiated from
the horn radiator 8 and EM waves received by the horn radiator 8
are focused into the second hollow conductor 2.
[0031] The first hollow conductor 2 is embodied in such a way that
first electromagnetic wave modes are producible in the first hollow
conductor 2 and the second hollow conductor 5 is embodied in such a
way that second electromagnetic wave modes are transferable in the
second hollow conductor 5.
[0032] The first and second hollow conductors 2, 5 are designed in
such a way that EM waves out-coupled from the first and second
coupling elements P1, P2 superimpose and radiate scattered and with
weak intensity from the horn radiator 8, respectively scattered and
weak intensity EM waves, which are received by the horn radiator 8,
couple into the first and second coupling elements P1, P2. EM waves
out-coupled solely from the first coupling element P1 radiate
focused and with strong intensity from the horn radiator 8, and
focused and strong intensity EM waves, which are received by the
horn radiator 8, couple to the first coupling element P1.
[0033] Furthermore, the first hollow conductor 2 is filled with a
first dielectric material and the second hollow conductor 5 is
filled with a second dielectric material. The first dielectric
material can be air from the environment. Alternatively, the first
hollow conductor can be evacuated. The second dielectric material
has a dielectric constant, which is 2.5-times greater than the
dielectric constant of the first material.
[0034] A separation S between the first and second coupling
elements P1, P2 in the transmission direction of the EM waves
equals 3/4.lamda.+n.times..lamda./2, wherein .lamda. is the
wavelength of the EM waves and n is a natural number 0, 1, 2, . . .
. A length of the first coupling element P1 amounts to .lamda./4
and a length of the second coupling element P2 amounts to
.lamda./2.
[0035] Furthermore, the apparatus 1 includes an electrical circuit
11 for operating the apparatus 1. The electrical circuit 11 will
now be described in greater detail. Leading from a first node K1 of
the second hollow conductor 5 to a second node K2 is a first
electrical line L1. A second line L2 connects the second node K2
with the second coupling element P2. A third line L3 connects the
second node K2 with a first inductance JS, wherein the first
inductance JS is connected via a diode DS to a third node K3. A
first capacitance CS is connected parallel to the first inductance
JS and the diode DS. The first capacitance CS and the first
inductance JS and the diode DS form together a bandpass filter
L5.
[0036] The third node K3 is connected via a second inductance JB
and a limiting resistor RV to a first terminal P3.
[0037] A fourth line L4 connects the first coupling element P1 with
a fourth node K4, wherein the fourth node K4 is connected to a
second terminal P4.
[0038] Via a second capacitance CB, the third node K3 is connected
with the fourth node K4.
[0039] The bandpass filter L5 forms with the second capacitance CB
a capacitive voltage divider 12. Size of the second capacitance CB
determines the powers sent to the first and second coupling
elements P1, P2. Due to the greater diameter of the second hollow
conductor 5, a higher mode is excited in the hollow conductor 5
than in the first hollow conductor 2. The higher mode of the second
hollow conductor 5 is expanded at the output of the horn antenna 8
to a broad lobe.
[0040] The bandpass filter L5 acts as a band blocking filter,
whereby no power reaches the second coupling element P2. The
limiting resistor RV is high resistance, whereby no power can drain
via the second terminal P4. The lengths of the first to fourth
lines L1-L4 are listed in the table below.
TABLE-US-00001 line/distance length/size (.lamda. = wavelength) S -
distance between the first 3/4 .lamda. + n * .lamda./2; n = 0, 1, 2
. . . and second coupling element L1 - first line antenna horn n *
.lamda./2 n = 1, 2, 3 . . . L2 - second line (n + 1/2) * .lamda. n
= 0, 1, 2 . . . L3 - third line (n + 1/2) * .lamda. n = 0, 1, 2 . .
. L4 - fourth line n * .lamda. n = 1, 2, 3 . . . travel path via
the bandpass filter L5 n * .lamda./2 n = 1, 2, 3 . . . length of
the second capacitance CB n * .lamda./2 n = 1, 2, 3 . . . length of
the first coupling element .ltoreq..lamda./4 length of the second
coupling element .ltoreq..lamda./4 or .ltoreq..lamda./2
[0041] In order to produce focused and strong intensity EM waves, a
high frequency signal HF is applied to the second terminal P4. The
high frequency signal HF is transferred via the fourth line L4 to
the first coupling element P1 and radiated monomodally (only one
mode is predominant in the radiation) via the horn radiator 8.
[0042] Placed on the first terminal P3 of the apparatus 1 is a
control voltage MV, which affects the cathode of the diode DS via
the limiting resistor RV and the second inductance JB. Since an
anode of the diode DS is connected via the first inductance JS and
the first line L1 with the second hollow conductor 5, and, from
there, with the third terminal P5 (signal ground potential), the
control voltage MV affects the diode DS. Because the control
voltage is acting in the reverse direction of the diode DS, only a
very smaller electrical current flows through the first line L1.
With voltage applied in the reverse direction, the diode DS acts as
a capacitance, whereby the bandpass filter L5 determines the pass
frequency for the operating frequency of the apparatus 1.
[0043] FIG. 2a shows the radiation of EM waves, which are
out-coupled only from the first coupling element P1 (one-mode
operation) and radiate focused and with strong intensity from the
horn radiator 8.
[0044] FIGS. 2b, 2c, and 2d each show radiations of EM waves, which
result from the superpositioning of the EM waves out-coupled from
the first and second coupling elements P1, P2 and from the design
of the voltage divider (see FIG. 1 and description for FIG. 1).
Switching between the radiation of FIG. 2a and the radiations of
FIGS. 2b, 2c, and 2d can occur by means of an analog or digital
control voltage MV.
[0045] FIG. 3 shows another embodiment, in the case of which the
voltage divider 12 is capacitive and formed only of CB and D1. In
this way, a stepless transition from the radiation of FIG. 2a to
the radiations of FIGS. 2b-d can be produced as a function of the
control voltage MV, wherein without applied control voltage MV the
radiation of FIG. 2a is achieved and with increasing control
voltage MV the radiation changes more and more in the direction of
the radiation of FIG. 2d. Since diode D1 is very high resistance,
and also in order to enable a fast switching from d) back to a), an
optional very high ohm (10 . . . 100 MOhm or more) resistor RU is
provided, through which the capacitance (in the range to a few pF)
formed with the diode D1 can be discharged.
[0046] FIG. 4 shows another embodiment of the apparatus of the
invention, which differs from the apparatus of FIG. 3 by a
simplified electrical circuit 11. Instead of an impedance-based,
capacitive voltage divider and bandpass filter or capacitance and
resonance circuit, the impedance-based voltage divider here is
formed of a diode D1 and the second capacitance CB. The second
capacitance CB represents a barrier for the control voltage MV
equivalent to the barrier provided by the diode D1. An inductance
JD connects the diode D1 with the signal ground potential on the
terminal P5. An apparatus of the invention with an electrical
circuit 11 is, as a whole, cost effective to implement.
[0047] In all examples of embodiments shown in FIGS. 1 to 4, the
transmission of EM waves of the apparatus 1 has been described. The
receiving of EM waves by the apparatus 1 is analogous to the
transmission of the EM waves.
LIST OF REFERENCE CHARACTERS
[0048] 1 apparatus [0049] 2 first hollow conductor [0050] 3 first
end face of the first hollow conductor [0051] 4 second end face of
the first hollow conductor [0052] 5 second hollow conductor [0053]
6 first end face of the second hollow conductor [0054] 7 second end
face of the second hollow conductor [0055] 8 horn radiator [0056] 9
first diameter [0057] 10 second diameter [0058] 11 electrical
circuit [0059] 12 voltage divider [0060] S separation [0061] P1
first coupling element [0062] P2 second coupling element [0063]
.lamda. wavelength of the EM wave [0064] n natural number 0, 1, 2,
. . . [0065] P3 first terminal [0066] P4 second terminal [0067] P5
third terminal [0068] DS diode [0069] CS first capacitance [0070]
JS first inductance [0071] CB second capacitance [0072] JB second
inductance [0073] RV limiting resistor [0074] K1 first node [0075]
K2 second node [0076] K3 third node [0077] K4 Fourth node [0078] L1
first line [0079] L2 second line [0080] L3 third line [0081] L4
fourth line [0082] L5 bandpass filter [0083] RU resistor [0084] JD
inductance
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